Just out of curiosity, I made an avatar for myself and actually had to resize it and use different saving settings to get it down to the proper size.

Sometimes, the program I was using (Adobe Photoshop CS) would guesstimate the wrong size after saving, and my picture would end up over the 20k we're allowed.

I ended up having to tell it to be 100x100 in my image program, and saved it as a .gif for a total of 17k in size. Oddly enough, windows reported it as 200x200 (well, close to it, like 197x197 or something). And it's bigger here than it was in my prog.

The moral of this story is... check the size of your file (both in kb and in pixel size). If you upload the wrong thing, it won't show. Took me around 5 tries to get it right.